Field of the Invention
The present invention relates to a grinding apparatus for grinding a workpiece held on a holding table while supplying grinding water to the workpiece.
Description of the Related Art
Plate-like workpieces such as semiconductor wafers or the like are ground to a predetermined thickness by a grinding apparatus (see, for example, Japanese Patent Laid-Open No. 2001-287141) and then divided by a cutting apparatus or the like into individual device chips, which will be used in various types of electronic devices or the like. The grinding apparatus has a holding table for holding a workpiece on its upper holding surface under suction, with a rotational shaft having an upper end coupled to the lower surface of the holding table.
The holding surface of the holding table is held in fluid communication with a suction source such as a vacuum generator or the like through a suction channel defined in the rotational shaft, for example. A suction force that is generated by the suction source is transmitted via the suction channel to the holding surface of the holding table, which holds the workpiece under the suction force on the holding surface. Between the holding table and the suction source, there is disposed a rotary joint (see, for example, Japanese Patent Laid-Open No. 2004-019912) for transmitting the suction force that generated by the suction source to the suction channel defined in the rotational shaft without leakage.